This invention relates to a precision fin indexing device for wind tunnel models and, more particularly, the invention is concerned with providing an indexing device capable of rapid positive attachment to aerodynamic surfaces on wind tunnel models at various angular positions relative to the model centerline in repeatable fashion with quick incremental changes of angular position.
One of the ways to test airborne structures such as ballistic missiles is to make a model of the missile and then attach fins to the model and test it in a wind tunnel. The fins are attached to the model at various places and oriented at various angles to the flow direction of the air in the wind tunnel. In order to accurately compare the models of the airborne structures, it is necessary that the angle of the fins be repeatable to the exact degree. Also, it would be desirable if the fin angle and position could be changed quickly and easily in fixed repeatable increments.
Heretofore, the common practice for positioning the fins at a particular angle, has been with an indexing protractor. The fins are set as near as possible to the correct angle and then clamped in place by fasteners passing through curved slots in the fin base. The positioning was approximate at best, and difficult, if not impossible, to repeat because of movement during clamping. Also the procedure was time consuming and required the efforts of skilled techicians to obtain anywhere near accurate results. Thus, it can be seen that there is a definite need for an indexing device which is capable of achieving repeatability of fin positions while producing quick incremental changes of position. Also, the device should allow the rapid positive attachment of aerodynamic surfaces on wind tunnel models at various angular positions relative to the model centerline in repeatable fashion.